A New View of Interstellar Dust as Revealed by Recent Observations Takashi Onaka (University of Tokyo) ASTRO-F®ISASSpitzer®NASA

Diffuse Emission from Galactic Plane Log S(W/m 2 /sr) COBE IRTS/MIRS Thermal Emission (submicron dust) Wavelength (  m) Excess emission (stochastically heated very small grains) UIR bands (~PAHs)

Outline Systematic variations in the UIR band features in the Galactic plane Characteristics of the MIR excess emission Solid features in the diffuse IR emission other than the UIR bands X-ray observations of interstellar dust Future prospects

PHT-S results of Galactic plane Wavelength (  m) Surface Brightness (10 -6 W m -2 mm -1 sr -1 ) Kahanpää et al. (2003) A&A 405, 999 No systematic variations in the UIR bands on GP l = ±5, ±15, ±30, ±60 & b = 0, ±1 (49 quiet regions)

IRAS100  m & UIR7.7  m Area I l ~ -10 Area II l ~ +50 Area III l ~ -130 Area IV l ~ +170 IRAS100  m UIR7.7  m Sakon et al. (2004) ApJ, 609, 203 Good correlation between UIR & 100  m

Typical spectra Wavelength (  m) Surface Brightness (x10 -7 W m -2 mm -1 sr -1 ) Area IArea II Area IIIArea IV

UIR/FIR ratio UIR/FIR Wavelength (  m) inner outer UIR/FIR larger in the outer Galactic plane -> Difference in destruction/formation balance

Shifts in peak wavelengths Wavelength (  m) Relative Number Peak shifts -> Profile variation (more tails at longer wavelengths in the inner Galaxy) 13 C effects or excitation and/or inclusion effects 6.2  m band 11.3  m band

Correlation with radiation field U 12  m & UIR7.7  m band U F /FIR UIR7.7  m/FIR F (12  m)/FIR W51 & G.C. (IRTS) Carina (ISO)

25  m/FIR U F /FIR F (25  m)/FIR ∝ U Stochastic heating model

60  m/FIR F (60  m)/FIR ∝ U U F /FIR

Correlation of excess emission with U Observations: Excess/FIR ∝ U (25 & 60  m) Multiphoton excitation cannot account for the observations because of the very broad nature of the excess emission Superposition of different radiation field components in the line-of-sight (Tokura et al. in preparation) (Dale et al. 2001, ApJ 549, 215) f(U, ) : emission with a particular U

25  m/FIR T(K) F /FIR Umin=0.1Umin=100 Umax=10 5 Umax=10 4 Umax=10 5 Umax=10 4

60  m/FIR T(K) F /FIR

12  m/FIR T(K) F /FIR MIR-FIR SED Good measure for the physical conditions & active region fraction (for galaxies)

65  m & 90  m features Wavelength (  m) Surface Brightness (x10 -6 Wm -2  m -1 sr -1 ) Onaka & Okada (2003) ApJ, 585, 872 Sharpless 171 region

65  m feature & diopside Wavelength (  m) Surface Brightness (x10 -6 Wm -2  m -1 sr -1 ) Diopside (CaMgSi 2 O 6 )

65  m feature versus temperature  (65  m)/  (100  m) Okada et al. in preparation 65  m feature Volatile species?

90  m feature & carbon onion T(K) Flux/Continuum Possible candidate: Carbon onion or curved graphite sheet

Oxygen K edge structure Takei et al (2002) ApJ, 581, 307 Cyg X-2 Gas/Dust abundance can be estimated From X-ray Spectroscopy Gas/Dust ~( )

X-ray Absorption Fine Structure Ueda et al. (2005) ApJ, 620, 274 Si XAFS GX13+1 Silicates XAFS Estimate of dust abundance & Diagnostic of chemical state of element in solid phase Fe metal or oxide? -> ASTRO-E2

ASTRO-F All-sky survey in 4 bands in FIR (  m) + 2 bands in MIR (5-26  m) 70cm cooled telescope Sun synchronous orbit Target launch: 2006 Two instruments on board IRC (2-26  m) & FIS (  m) Pointed observations 9 bands in NIR-MIR 4 bands in FIR Spectroscopy in NIR-FIR (2-26  m;  m)

ASTRO-F observations of interstellar dust Wavelength (  m) Log S(W/m 2 /sr) ASTRO-F can separate each emission component IRACMIPS IRC FIS